Bovine serum is commonly used in mammalian cell culture to promote cell growth and protein production. Since serum is expensive, non-defined animal materials such as primatone and albumin have been used as serum replacements. However, the quality of these non-defined animal proteins varies from batch to batch and consistent cell growth in these media is difficult to achieve. Moreover, pathogens such as prions and viruses have been identified as potential infectious agents (Balter, M. 2000, Kozak et al. 1996) that may reside in those animal derived products. Many regulations now strongly address these concerns about using serum or non-defined animal proteins in mammalian cells.
To support the growth of animal cells, a variety of components are essential to be included in the culture media. For example, glutamine and glucose are basic energy sources that support animal cell growth. Breakdown of these compounds provides resources for energy-generating pathways, the TCA cycle and glycolysis. The byproducts of these pathways are also the building blocks or sources for bio polymer synthesis (Petch and Bulter 1994). In addition, vitamins, amino acids and growth factors are also essential for robust cell growth by either supressing the cascade of the suicide pathway known as apoptosis or by promoting the progression of the cell cycle so that cells may replicate (Franek F. 1994, Murakami et al. 1982, Mastrangelo et al. 1999, Xie and Wang, 1996, Muhamed Al-Rubeai 1998).
Trace elements are also important for the growth of animal cells. Ham and McKeehan (1979) noticed that adding trace elements, such as Zinc, iron, selenium, copper, molybdenum, and manganese, etc., was important for cloning and continuous passage of animal cells in stringent conditions of serum-free media. Regardless, the importance of supplementing trace elements in the media for animal cells has not been well addressed (Schneider 1989, Merten and Litwin 1991). This may be due to the assumption that trace elements existed as contaminated impurities within serum or non-defined animal derived materials already.
Accordingly, there is also a need to provide chemically defined media for cell culture and/or production of heterologous proteins in commercially useful amounts.